1. Technical Field of the Invention
This invention relates to pulse responsive devices and more particularly but not solely to pulse rate meters and pulse oximetry devices.
2. Description of the Prior Art
Pulse oximetry devices, and some other pulse responsive devices, utilise the effect that there is a change in the light transmitted through or reflected from body tissues, due to the pulsing of the blood flow or flow of other body fluid. Such pulse responsive devices include light sensors which produce electrical output signals which can be analyzed to determine various parameters such as pulse rate or blood oxygen saturation for example. Advantages of these devices are that they are non-invasive and they can monitor the relevant parameter on a continuous basis. However, we have found that movements of the body can generate spurious noise in the output signal of the light sensor, thus masking the signal which is to be monitored. We have now devised a device which overcomes this problem.